01Gradient shift

<main class="stage">
  <p class="hint">Hero background</p>
</main>

@use "../../../../site/static/demo-tokens" as *;

// ── 변수 3개. 변형은 이것만 바꾼다 ──────────────────────────
$duration: $dur-loop;                                // 그라데이션이 한 바퀴 흐르는 시간
$easing: $ease-out;
$color: $subject-blue;                                // 흐르는 그라데이션의 포인트 색

// ── 데모 무대 ──────────────────────────────────────────
@include stage($stage-ink);

.stage {
  position: relative;
  overflow: hidden;
}

// 실제 배경은 스테이지보다 두 배 크게 깔고 background-position 만 움직인다 (transform·opacity 만 쓰는 규칙의 배경판)
.stage::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: linear-gradient(120deg, $stage-ink, $color, $subject-cream, $stage-ink);
  background-size: 220% 220%;
  animation: flow $duration $easing infinite;
}

.hint {
  position: relative;
  margin: 0;
  padding: 10px 20px;
  border-radius: $r-pill;
  background: rgba($stage-ink, .35);
  color: $stage-paper;
  font: 700 clamp(14px, 4vw, 18px)/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

@keyframes flow {
  0%   { background-position: 0% 50%; }
  50%  { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

// ── 접근성: 움직임 줄이기 설정이면 정지 프레임만 ────────────
@media (prefers-reduced-motion: reduce) {
  .stage::before { animation: none; background-position: 0% 50%; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.stage {
  position: relative;
  overflow: hidden;
}

.stage::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: linear-gradient(120deg, #17141a, #2f6df6, #fff7e6, #17141a);
  background-size: 220% 220%;
  animation: flow 2s ease-out infinite;
}

.hint {
  position: relative;
  margin: 0;
  padding: 10px 20px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.35);
  color: #ffffff;
  font: 700 clamp(14px, 4vw, 18px)/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

@keyframes flow {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}
@media (prefers-reduced-motion: reduce) {
  .stage::before {
    animation: none;
    background-position: 0% 50%;
  }
}

import type { CSSProperties, ReactNode } from "react";
import styles from "./GradientShiftBg.module.scss";

export type GradientShiftBgProps = {
  children?: ReactNode;
  /** 한 바퀴 흐르는 시간 (기본 2000ms) */
  duration?: number;
  easing?: string;
  /** 흐르는 그라데이션의 포인트 색 */
  color?: string;
  className?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

export default function GradientShiftBg({
  children,
  duration = 2000,
  easing = "ease-out",
  color = "#2f6df6",
  className = "",
}: GradientShiftBgProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  return (
    <div className={`${styles.stage} ${className}`} style={vars}>
      <div className={styles.bg} aria-hidden="true" />
      {children}
    </div>
  );
}